Evidence for Himalayan remagnetization in Tarim Basin

Himalayan remagnetization in the Tarim Basin was found to be widespread in Paleozoic, Mesozoic and Cenozoic rocks. Rock magnetism was performed to study the magnetic carriers. The authors believe that tectonic fluid in the Himalayan stage caused the rock remagnetization. The framboidal pyrites in bitumen and hydrocarbon-rich rocks may transform to framboidal magnetite in the later alkali environment, which leads to remagnetization.     

Magma flow inferred from magnetic fabrics in Wanning gabbro pluton and diabase dykes, Hainan

Measurements of anisotropy of magnetic susceptibility (AMS) were performed on a gabbro pluton and 7 diabase dykes in the Wanning area, southeast Hainan Island. Rock magnetism showed that pseudo-single domain (PSD) to multidomain (MD) Ti-poor magnetite carries the magnetic fabric in the gabbro pluton whereas MD Ti-poor magnetite carries the magnetic fabric in the diabase dykes. The corrected anisotropy degree (Pj ) in most specimens was found to be less than 1.2 which is indicative of a possible flow-related magnetic fabric. The AMS eigenvectors within each site are generally well grouped. The maximum susceptibility axes (K1 ) of the gabbro pluton are inclined towards the north at low angles (< 30°). K1 axes of the diabase dykes are inclined towards the NNW and SSE with dip angles of ≤ 30°. From this study, it appears that the emplacement mode of the gabbro pluton was characterized by intrusion from the north to the south at a low angle whereas the diabase dykes were emplaced from the NNW to the SSE at low to moderate angles. This was verified by comparison of the rock fabric to the magnetic fabric. All of this evidence leads to the conclusion that the Wanning gabbro pluton and diabase dykes were the products of pulsative intrusion from the same magma chamber in the area far to the north of Wanning, which suggests that basic rocks may exist beneath the Indosin- ian granite in the area to the north of Wanning.     

磁性参数的环境指示意义

介绍了岩石磁学研究中常用的能够指示环境变迁和气候变化的几种磁性参数及其组合。研究表明：磁化率是气候变化的代用指标之一，其值的高低反映气候的暖冷和沉积颗粒的细粗，用参数HSIRM，Bcr,HSIRM/k可以识别磁性矿物类型，较多磁铁矿的存在指示暖湿的沉积环境，反映沉积物颗粒细；而较多赤铁矿的存在则指示干冷的沉积环境，反映沉积物颗粒粗。HARM，Ber,HSIRM/k，S比(HSIRM-100mT/HSIRM)在环境监测中有重要的意义。     

Magnetic properties of surface soils across the southern Tarim Basin and their relationship with climate and source materials

The magnetic susceptibility (χ) of surface soils on the Chinese Loess Plateau (CLP) has strong positive correlation with mean annual precipitation.It is widely accepted that ultrafine magnetite/maghemite grains produced during pedogenesis are responsible for the enhancement of χ,and loess χ on the CLP has been widely used as a proxy for the intensity of the East Asian summer monsoon.However,few works have investigated mechanisms for the enhancement of χ in the case of surface aeolian sediments in westerly-dominated inland China,north of the Tibetan Plateau.Here detailed rock magnetism and grain size studies of 49 surface samples taken across the southern Tarim Basin for different rainfall/temperature/altitude conditions are presented.The results show that samples taken from desert have the lowest χ values and that χ of loessic sand and loess samples decreases with increasing altitude.In addition,the rock magnetism studies suggest that the magnetic properties of surface soils across the southern Tarim Basin are mainly controlled by the concentration of coarse aeolian ferrimagnetic minerals.The contribution of ultrafine pedogenically produced magnetic grains to χ is very limited.     

几种不同类型金矿的高精度磁测异常特征

许多金矿的赋矿(或伴生)岩石与其周围岩石之间存在着磁性差异,如与中基性脉岩有关的金矿成因模式矿床、破碎蚀变火山岩型金矿等,在其上能观测到磁异常.即使是河床底部缝隙中与砂金相伴沉淀的重砂,由于铁磁性矿物含量较高,与其附近砂石之间存在磁性差异,利用高精度质子磁力仪,也能观测到比较明显的磁异常.在西藏自治区及四川省一些金矿床(点)上的研究取得了良好的进展,对砂金矿、锑金伴生型金矿,中基性脉岩型金矿上的高精度磁测异常特征有了新的认识,为利用高精度磁测方法间接寻找金矿积累了经验.     

Magnetic granulometry of recent sediments from the Huguang Maar and its implication for provenience

To understand the origin and its climatic implications of the Huguang Maar sediments, we conducted laser grain size analysis and rock mangtic measurement for the recent deposits from the Huguang Maar and for the volcanic rocks of the caldera for comparison. The grain size distributions are dominated by clayey silts for both the bulk sediments and magnetic separates. Acquisition of isothermal remanent magnetization (IRM) and thermal demagnetization of IRM suggest (titano) magnetite as the dominating magnetic mineral in the sediments; high coercivity minerals are not detected. Therefore, the ratio of the susceptibility of anhysteretic remanent magnetization (k _ARM) to the weak field magnetic susceptibility (k), k _ARM/k can be used to estimate the grain size of magnetite. The sediments and volcanic rocks yield values of 13.7 and 11.8 for the k _ARM/_k, respectively, corresponding to grain size values of ～0.03 µm and ～0.05 µm. The magnetic granulometry of lake sediments is distinctive from one of the Chinese loess, in which published data suggest a value of 6.0 for k _ARM/_k, and grain size of ～0.1 µm, but is akin to the nearby volcanic rocks. Although a Loess Plateau source of the lake sediments cannot be fully ruled out, the catchment is most probably the main source. We explain the slightly finer magnetite grain size in sediments than in the volcanic rocks as being disintegrated of particles during erosion and transportation. We conclude that there is no evidence for aeolian input of the Loess Plateau dusts into the Huguang Maar, and the relationship between magnetic parameters of the lake sediments and winter monsoon intensity is probably more complicated than previously thought.     

单畴磁铁矿磁接收器磁学模型

很多生物可以利用地磁场辨别方向和方位,而生物磁铁矿被广泛发现存在于这些生物体中,研究者认为,生物磁铁矿与周围组织(包括神经组织)构成磁接收器,它在与外界磁场的相互作用中,将外界磁场信息转化成神经信息促使生物作出相应的反应;生物磁铁矿磁接收器理论包括单畴磁铁矿磁接收器模型和超顺磁磁铁矿磁接收器模型;趋磁细菌体内存在典型的单畴磁铁矿颗粒,本文中,以趋磁细菌为例,从磁学理论角度出发,定性的探讨了单畴磁铁矿磁接收器的磁学模型和工作机制:在外磁场中,外面包围着生物膜的单畴晶体会受到力的作用,单畴晶体把力转加给生物膜,再被生物膜中的机械感受器接收到,再转变为刺激信号,引起细胞相应的运动行为;或者是,磁铁矿粒子通过与生物膜的结合,把受到的力转变为打开或关闭离子通道,影响离子的流入,跨膜电势发生改变,从而产生刺激信号;多个单畴晶体及膜的存在会导致信号的增加与放大.     

兰州地区晚新生代沉积的岩石磁学记录及其古环境意义

位于黄土高原和西北干旱区过渡带的兰州地区,在晚新生代发育了一套风成红黏土和冲积—河湖相沉积.这套地层详细的岩石磁学研究结果表明,磁化率等一些磁学参数在细节上可能反映成壤作用强弱,但在大的趋势上大致反映干旱化,在长尺度研究中可作为干旱化的指标.S-300mT等另一些磁学参数主要反映赤铁矿质量分数,与红度值明显相关,因此同红度一样可作为温度的指标.底部冲积一河湖相沉积中黏土的主要载磁矿物是磁铁矿和赤铁矿;中下部红黏土沉积的主要载磁矿物是磁赤铁矿和赤铁矿,可能含针铁矿;中上部红黏土主要的载磁矿物是磁赤铁矿、磁铁矿和赤铁矿,可能含针铁矿.利用岩石磁学恢复的古环境表明,兰州地区在8.35～7.2 Ma是一个较为温暖的以冲洪积和河湖相为主的沉积环境;7.2～3.5 Ma主要为干陆地环境,同主体黄土高原一样接受粉尘沉积;6.3 Ma风尘沉积在沉积物中开始占主导地位;5.2 Ma兰州及其周边地区发生了急剧干旱化,可能伴随着快速降温;3.5 Ma开始的青藏高原运动A幕使兰州盆地瓦解,并于1.4 Ma开始接受黄土沉积,成为了黄土高原的西缘部分.     

Rock magnetism and magnetic anisotropy in folded sills and basaltic flows: A case study of volcanics from the Taimyr Peninsula,Northern Russia

Magnetic measurements were performed on apparently deformed igneous rocks of 23 sites from the southeastern part of the Taimyr Peninsula. Rock magnetism and reflected light microscopy analyses reveal that fine-grained titsnomagnetites up to pure magnetites mainly carry the majority of magnetic fabrics in the sills, and that the slightly coarser Ti-poor or -medium titsnomagnetites carry most mag-netic fabrics in the basaltic flows. Magnetic anisotropies were determined by applying anisotropy of low-field magnetic susceptibility （AMS） on 180 unheated samples and 128 samples that had been pre-viously heated to 600℃ during a paleomagnetic study to detect heating effects on the anisotropy of magnetic susceptibility （AMS） properties of volcanic rocks. Laboratory heating significantly affects anisotropy variations of these igneous rocks corresponding to the mineralogical changes during the heat treatment.     

利用神经网络预测油气层损害

利用人工神经网络预测油气层敏感性参数，根据大港油田的油气层岩石物性参数、岩石学分析参数以及油气层岩石敏感性参数等历史资料，训练神经网络，以此神经网络预测某些油气层的敏感性参数，该方法能迅速、准确地预测未来指定油气层的敏感性参数，为保护油气层提供依据。     

Improved Marquardt Algorithm for Training Neural Networks for Chemical Process Modeling

IntroductionResearch on artificial neural networks(ANN) hasmade great progress during the past few years.Neural networks have been widely used in chemicalprocesses.Among all kinds of networks,the back-propagation (BP) network is the most commonchoice forits high capability of nonlinear mapping,study and classification. Through adjustingnetwork weights according to samples,the BPnetwork can simulate systems with complexnonlinear mapping relationships,such as chemicalprocesses.　The most com…     

韩家岭隧道围岩物理力学参数反分析

基于差分法、正交设计和人工神经网络建立了新的隧道围岩物理力学参数反分析方法·按照正交设计要求选取不同物理力学参数,用FLAC差分程序计算得出相应的神经网络分析样本;进行网络训练和网络结构及学习参数优化;利用现场监测数据,对韩家岭隧道围岩物理力学参数进行神经网络反分析,分析结果满足精度要求·     

Rock magnetic studies on the hominoid-bearing sediments at Zhupeng, Yuanmou Basin, southwestern China and its paleoclimatic significance

It has been proposed that paleoclimatic changes and tectonic events strongly affect hominoid evolution. The Zhupeng section at Yuanmou Basin, southwestern China, with the hominoid-bearing fluvial-lacustrine sediments, is an ideal natural laboratory to test this hypothesis. This study provided an integrated magnetic study, including low-frequency susceptibility, the anisotropy of magnetic susceptibility, temperature-dependent susceptibility, hysteresis loops, isothermal remanent magnetization, and anhysteretic remanent magnetization, on samples from the Baozidongqing section at Zhupeng. Results show that the dominant mag- netic carrier is hematite, with minor amount of magnetite. Both the composition and concentration of magnetic miner- als strongly correlate with the lithostratigraphy. At least eight short-term events defined by higher concentrations of magnetite were identified. These short events reflect that the subtropical dry-hot climate is similar to today＇s climate. Basing on the lithostratigraphic and rock magnetic results, we suggest that Yuanmou Basin was in a steady deposition environment from about 11 to 7 Ma, which is characterized by alternating of long-term torrid-humid climate and short-term dry-hot climate. Our study provides invaluable environment information for understanding the climate shift and the relationship between paleoenvironment and hominoid evolution in southwestern China during late Miocene.     

福建尤溪梅仙地区马面山群变质岩原岩恢复及其与铅锌成矿的关系

通过变质岩产状、矿物组合及组构特征、矿物间的交代关系、典型矿物空间分布特征、岩石化学、稀土元素化学等方面对原岩恢复进行研究。研究结果表明:丁家山铅锌矿区新元古代马面山群变质岩均为副变质岩,其中石英云母系列变质岩的原岩为泥质粉砂岩和粉砂质泥岩,石榴子石绿帘石透辉石系列变质岩原岩为钙质泥岩、钙质泥质粉砂岩、钙质粉砂质泥岩、泥灰岩等富钙质岩类,而大理岩类的变质原岩为钙镁质沉积岩;丁家山铅锌矿为马面山群龙北溪组上段经加里东期区域变质的富钙质沉积岩与燕山期花岗岩发生接触交代作用而形成的矽卡岩型矿床,矿区广泛存在的石榴子石、透辉石、绿帘石等非金属矿物与磁铁矿、磁黄铁矿、黄铁矿、闪锌矿和方铅矿等金属矿物同为接触交代变质作用在不同阶段的产物。     

Magnetic properties of highroad-side pine tree leaves in Beijing and their environmental significance

This is a report on magnetic properties of highroad-side tree (Pinus pumila Regel) leaves collected along an expressway linking Beijing City and the Capital International Airport and further focus on their environmental contributions. A series of rock magnetic experiments show that the primary mag-netic mineral of leaf samples was identified to be magnetite,in the pseudo-single domain (PSD) grain size range 0.2―5.0 μm. On the other hand,magnet-ite concentration and grain size in leaves are ascer-tained to decrease with increasing of sampling dis-tance to highroad asphalt surface,suggesting that high magnetic response to traffic pollution is localized within a distance of some two meters away from highroad asphalt surface. Although magnetic suscep-tibility is ordinarily regarded as a simple,rapid and low-cost method for monitoring traffic pollution,saturation isothermal remanent magnetization (SIRM) can be treated as a valid proxy for monitoring air par-ticulate matter (PM) when samples are magnetically weak. It is believed that a synthetic rock magnetic study is an effective method for determining concen-tration and grain size of ferromagnets in the atmos-pheric PM,and then it should be a rapid and feasible technique for monitoring atmospheric pollution.     

Effects of the grain size distribution on magnetic properties of magnetite: constraints from micromagnetic modeling

Magnetite is the most important magnetic mineral in paleomagnetism. Its magnetic properties are controlled by many factors, such as grain size distribution, shape and interactions. Traditional rock magnetic experiments, however, have great difficulty in decoupling the effects of these parameters. In this study, we attempted to investigate the effects of grain size distribution on magnetic properties of magnetite powders by using a micromagnetic method. The particle geometries used in the micromagnetic model were based on the grain size distribution observed in a synthetic magnetite powder. The simulated hysteresis parameters agree well with the experimental measurements and provide clear microstructures of the magnetic remanence. Our results show that grain size plays a more important role in affecting hysteresis parameters of magnetite assemblages than shape under effects of interactions. Uniform or vortex superstates formed by two or more particles are found and display different stabilities of magnetic recording in assemblages. Some domain structures of single-domain （SD） particles are reversed as the applied field decreases to zero. Small pseudo-single-domain particles behave as SD structures and may dominate the magnetic recordings. In all, micromagnetic modeling of grain size distributions provide a better understanding of magnetic assemblages consisting of nanoscale particles.     

新疆北部地区岩石生热率分布特征

在大量岩石样品分析数据和研究成果的基础上,系统分析了新疆北部地区不同时代、不同岩性和不同大地构造单元岩石生热率的分布特征,讨论了岩石生热率与大地构造单元地质特征之间的关系．根据岩石中 Ｋ、 Ｔｈ 、 Ｕ 的含量和地壳各结构层的岩石组成,计算了地壳各壳层放射性生热元素的含量,系统研究了新疆北部地区岩石与各时代地层的平均生热率及其变化．岩石生热率分布在一定程度上反映了区域基底生热元素的丰度和岩浆活动的强度．对不同体系生热元素的时空分布与地球化学特征进行了探讨     

超顺磁磁铁矿磁接收器磁学模型

生物磁铁矿磁接收器理论模型包括单畴磁铁矿磁接收器模型和超顺磁磁铁矿磁接收器模型.蜜蜂体内存在典型的超顺磁磁铁矿颗粒.本文以蜜蜂为例,从磁学理论角度出发,定性的探讨了超顺磁磁铁矿磁接收器的磁学模型和工作机制.在外磁场作用下,每个超顺磁颗粒会受到力的作用,同时伴随着尺寸沿着一定方向的收缩和扩张.超顺磁颗粒把力以及扩张收缩作用传递给外面的生物膜及生物骨架(埋藏在神经系统中)从而产生相应的神经信号,而多个超顺磁颗粒磁接收系统的存在会放大和加强信号的产生.     

内蒙古阿拉善左旗查干德日斯超贫磁铁矿地质、磁异常特征:对阿拉善地块火山沉积变质型铁矿资源前景的指示

矿区查干德日斯位于阿拉善地块巴音乌拉山断隆东缘。野外地质、地球物理勘探工作表明该地区存在较大规模的超贫磁铁矿,磁铁矿体TFe平均含量为14.04%(12.32%~14.98%),m Fe 6.55%(5.32%~7.47%)。该磁铁矿主要赋存于灰黑色斜长角闪片麻岩,具明显层控特点,赋矿原岩应为富铁基性火山岩建造,由区域中-深程度变质作用形成,属火山沉积变质型铁矿床。类比阿拉善地块区域磁场特征认为,阿拉善地块弱磁结晶基底中广泛分布的斜长角闪片麻岩类为寻找超贫磁铁矿提供巨大的找矿空间。